Structures such as buildings and bridges comprise various sections to make up the floors, walls, support beams, the roadway, and the like. These various sections are sometimes spaced apart from each other to form gaps that are referred to as expansion joints or simply joints. These joints can be either expansion joints, i.e. voids designed to accommodate expansion and contraction typically caused by temperature change, or seismic joints, which are voids designed to accommodate expansion and contraction due to earthquakes.
Building codes require fire protection for buildings and accordingly, these joints must provide fire protection to prevent fire from spreading from floor to floor or room to room. Typically the joints will be covered with a plate that serves as a cover to allow normal passage over the joint. A fire blanket hangs under the plate between the two sections that form the joint and within the joint. Generally, the fire blanket will comprise a first layer that hangs lowest within the joint and is typically made of a flame retardant material such as zetex, zseal or zelex HT. A second layer will lie on top of the first layer and is generally made of a thermal resistant material, such as Refrasil.RTM., The Carborundum Company, Fibers Division, P.O. Box 808, Niagara Falls, N.Y. 14302-0808, that impedes heat flow. A third layer is used as an insulator and typically is made of a fabric such as kaowool. A fourth layer is often used on top of the third layer, or what is termed the "cold side," and is generally made of zetex. All four layers are generally stapled together to form the fire blanket. However, the middle two layers do not extend outward as far as the first and fourth layers. These outer portions are generally referred to as "ears" and are approximately two inches in width. The blanket is stapled together at the ear and the ears are used to mount the blanket to the two adjoining sections, such as abutting sections of a floor, that form the joint. The blanket is generally attached to the abutting sections with nails and L-shaped brackets that run lengthwise along the sections. The fire blanket is mounted within the joint in such a manner that it literally hangs down into the joint in a U-shape and thus provides more width within the blanket than is necessary to cover the joint.
Problems occur when the abutting sections move relative to each other due to sway within the structure that contains them, i.e. sway of the building due to an earthquake, or expansion of the sections due to temperature. When the sections move vertically with respect to each other, or, horizontally toward or away from each other, there generally is no problem with respect to the fire blanket due to the fact that the blanket is wider than necessary to cover the joint. However, when the sections shear with respect to each other (for example when the pieces move horizontally but laterally with respect to each other), the force can tear the blanket thus compromising effectiveness of the joint cover against the spread of fire.
An attempt to protect against damage to the fire blanket due to lateral shear utilizes a sliding rail-type system. This system is called "3-D Movement" and is described and illustrated in the catalog of Balco/Metalines, 2626 South Sheridan, Wichita, Kans. It involves utilizing a bracket to attach a vertical section of a fire blanket to one corner of, for example, an abutting floor section that with a second abutting floor section forms a joint. The bracket runs continuously lengthwise along the section and has a continuous, laterally extending, upturned "hook" portion covering a top portion of the fire blanket. A second section of fire blanket is attached to a parallel and opposing corner of the second floor with an L-shaped bracket. This second portion of fire blanket then has a continuous, laterally extending, down-turned "hook" attached to it opposite the L-shaped bracket. This down-turned "hook" is placed within the aforementioned upturned "hook" to form a seal and connect the two sections of fire blanket. The seal runs continuously along and just below the parallel corners of the oppositely disposed floor sections. The "hooks" can slide laterally with respect to one another thereby accommodating the lateral shear of the two abutting floor sections. This system, however, greatly increases the cost of the joint cover because of the extra cost associated with the hook portions, as well as the extra labor involved. Additionally, the seal may breach from the weight of the second portion of fire blanket which can move due to thermal currents during a fire.
An expansion joint cover is therefore needed which overcomes the shortcomings of the prior art.